In many food preparation facilities, such as commercial kitchens and restaurants, the sink is a major tool used for disposing of various types of food waste. In some cases liquid food wastes, such as fats, oils and grease are poured down the sink, and in other cases a mechanical device such as a garbage disposal is used to shred the food waste as it leaves the sink and enters the wastewater system. Many food preparation establishments, such as commercial restaurants and the like, have multiple sinks for such food waste disposal.
In many jurisdictions, the disposal from commercial kitchens of floating food wastes such as Fats, Oils and Greases (FOG) into the sanitary sewage system is prohibited. There are a number of reasons why this is so, including the ability of those types of materials to clog or plug sanitary sewage systems and the difficulty of adequately treating such materials in a sewage treatment facility. Therefore, many jurisdictions require that these materials be removed from the wastewater stream before permitting the wastewater stream to be added to the sanitary sewer system.
As a result, devices known as grease interceptors have been developed. These grease interceptors are hydraulically connected to the wastewater outflow stream from the food preparation kitchen or other facility and are located before the sanitary sewer, typically within the kitchen. The grease interceptors may take a number of forms, but typically consist of an in-line container which is mounted at or below grade on the wastewater outflow line downstream of all of the sinks and the like. The container includes features that are configured to allow fats, oils and grease to float to the surface of the container where they can be skimmed off and physically removed to a landfill site.
In some circumstances larger sized grease interceptors which may be positioned outside of the building foot print to capture FOG before it can leave the property of the food service establishment are appropriate. Such larger scale devices have some advantages, including separating the device, which can emit very foul odours when being emptied, from the inside of the kitchen; permitting a larger volume device to be used because there is no concern about fitting into a restrictive building floor plan; and extending the time between service calls, because the interceptors can be made to contain much larger volumes. As well by being outside, services such as pump out trucks can come and go easily without disturbing the patrons of the food service establishment.
An issue with such large scale interceptors is the design of the components and fittings that are suitable for reliably separating the water from the FOG and any solids which might be found in the waste water. In general, in larger scale interceptors they will be permanently installed, below grade, which can make them more difficult to properly clean out when being serviced. In general the solids tend to sink while the FOG tends to float leaving the water in the middle. What is required is an easily assembled system or assembly which can reliably allow water to flow out of the grease trap while preventing the passing of either solids or FOG. Typically, in the prior art, an overflow weir is used to contain the heavier than water solids in one part of the tank and an underflow weir is used to control the lighter than water floating waste such as FOG. However the use of such weirs can create cleaning problems as the waste material, particularly the floating FOG can tend to spread out throughout the interceptor as the liquid level is lowered, for example, during a pumping clean out. The weirs can create closed spaces into which such semisolid wastes can flow and which can be very difficult to properly clean from the outside. Examples of prior art devices can be found in the following prior patents and applications:
U.S. Pat. No. 6,645,387;
U.S. Pat. No. 6,951,619;
U.S. Pat. No. 7,367,459;
U.S. Pat. No. 7,540,967;
U.S. Pat. No. 7,641,805; and
U.S. Pat. No. 8,252,188.
What is desired is a simple and effective outflow path from the body of the permanently installed interceptor for the separated water. The outflow path should be configured to reduce the chance of solids, settling from above the outtake point from being allowed to be removed with the water. The outflow path should also be configured to prevent other materials such as buoyant or semi buoyant FOG from being allowed to follow the water through the outflow path. Preferably such an assembly would be easy to clean and simple to fabricate and use. Most preferably, such an outflow path can be made of easy to assemble and disassemble components to facilitate effective washing or cleaning as is periodically required, having regard to the permanently installed condition of the interceptor tank. Further, the components which define the outflow path would not form any closed off spaces or voids into which wastes can settle and from which wastes can be difficult to clean.